Which of the following choices represents the Fischer projection of $C_2{H}_{6}O$ (ethanol)?

• A. $H|C—\mathrm{OH}|H$
• B. $H|C—\mathrm{OH}|\mathrm{CH}{3}_{}$
• C. $\mathrm{CH}{3}_{}|C—\mathrm{OH}|H$
• D. $\mathrm{OH}|C—H|\mathrm{CH}{3}_{}$

Answer: (B)

Verified step by step guidance

1. Step 1: Identify the molecular structure of ethanol (C2H6O). Ethanol consists of a two-carbon chain where one carbon is bonded to an -OH group (hydroxyl) and the other carbon is bonded to hydrogens and a methyl group (CH3).
2. Step 2: Understand the Fischer projection conventions. In a Fischer projection, the vertical lines represent bonds going away from the viewer (into the plane), and the horizontal lines represent bonds coming out toward the viewer. The central carbon is at the intersection of these lines.
3. Step 3: Assign the substituents around the central carbon (C2) in ethanol. The carbon bonded to the -OH group should have the hydroxyl group (OH), a hydrogen (H), and a methyl group (CH3) attached.
4. Step 4: Arrange the groups in the Fischer projection so that the vertical bonds are to the carbon chain (up and down), and the horizontal bonds are to the substituents (left and right). For ethanol, the carbon chain is just two carbons, so one side will have the methyl group (CH3), the other side will have the hydrogen (H), and the vertical positions will be the hydroxyl (OH) and hydrogen (H).
5. Step 5: Verify that the Fischer projection correctly represents ethanol by checking that the central carbon has four different groups arranged properly: OH, H, CH3, and the other carbon (or hydrogen) as appropriate. This confirms the correct Fischer projection among the given choices.